Looking to expand my "creative abilities" lens wise. I have my Sigma 18-250mm 3.5-6.3 as a "walk around" lens. I have my 50mm 1.8 indoor portrait lens. Now I want to go macro. Wide angle will be later on....

Looking around, I have found the Nikkor 105mm 2.8 Micro to be the "it" lens. My question is, does the VR option make it worth ~$300+ more? Are there any other differences in say image sharpness, build quality or AF IQ/speed? I would also be using this as a portrait lens along side the 50mm.

My budget is not tight, but I am not independently wealthy either- best bang for the buck comes to mind....

To me, the VR is pretty much useless on this lens. Believe it or not, the closer you get to 1:1, the less effective the VR is. Why they did this, I have no idea, but you'd think that is where you'd want it most.
As far as focus, almost all people use manual focus for macro, so AF speed isn't really a concern there (or for portraits).
And with IQ, I'd put my older 105mm f/2.8 AF-D up against the new lens anytime, at half the price.

For macro work, I think having a tripod would be the best bet for clear, sharp pictures. The VR feature is useless if you are going to use a tripod. Unless that is, you already have super duper steady hands.

I don't think I've ever heard anything bad about the Sigma, so that is a viable option, but I think I would still try to steer you towards the AF-D. One, I know the IQ that it is capable of, and I see good glass as much as an investment. You can pick up a VG copy of the AF-D for the price of the Sigma, and it will hold value much better in the long run.